As one type of a vehicle brake device, a device which is disclosed in a Patent Literature 1 is known. As shown in FIG. 1 of the Patent Literature 1, the vehicle brake device includes a master cylinder 1 wherein master pistons 113 and 114 are driven to move by a servo pressure in a servo chamber 127 and by the movement of the master pistons, master pressure in the master chambers 132 and 136 changes, a mechanical type servo pressure generating device 44 connected to a high pressure source 431 and the servo chamber to generate the servo pressure in the servo chamber corresponding to the pilot pressure generated in a pilot chamber based on the brake hydraulic pressure of the high pressure source, an electric pilot pressure generating device 41, 42, 43 connected to the pilot chamber for generating a desired pilot pressure in the pilot chamber, a master-pilot connecting brake fluid passage 511 which connects the master chamber and the pilot chamber, and a brake actuator 53 which performs an ABS control and an ESC control and so on. The master-pilot connecting brake fluid passage is a passage branched from the master-wheel connecting passage 51 which connects the master chamber and the wheel cylinder 541, etc. The vehicle brake device includes a pressure sensor 74 which detects the servo pressure.
Generally, in a vehicle brake device as structured above, a target servo pressure is set which corresponds to the stroke amount of the brake pedal 115 when a normal braking operation is performed and then the pressure decreasing valve 41 and the pressure increasing valve 42 are controlled so that the target servo pressure and the actually detected servo pressure (actual servo pressure) agree with each other (feedback control). As the result, a master pressure which corresponds to the target servo pressure is outputted from the master cylinder and a wheel cylinder pressure which corresponds to the master pressure is applied to the wheel cylinders 541 through 544.
Further, the target servo pressure is set relatively a high pressure (for example, the maximum output pressure of the servo pressure generating device) when the ESC control (anti-skid control) or a TRC control (traction control) is performed. Accordingly, the servo pressure supplied from the servo pressure generating device 44 becomes relatively high and the pressure decreasing valve 41 and the pressure increasing valve 42 are feedback controlled to output the relatively high pressure master pressure from the master cylinder 1. Further, the holding valve and the pressure decreasing valve provided in the brake actuator 53 are controlled to apply desired wheel cylinder pressures individually to respective wheel cylinders. It is noted that a reason why the relatively high pressure is set as the target servo pressure is that by decreasing the operation number of times of the pressure decreasing valve 41 and the pressure increasing valve 42 (especially pressure increasing valve 42), long service life can be achieved for these control valves.